AWS Lambda to list EC2 instance id using python boto3

Question

I m trying to list out EC2 instance id using python boto3. I m new to python.

Below Code is working fine

import boto3
region = 'ap-south-1'
ec2 = boto3.client('ec2', region_name=region)

def lambda_handler(event, context):
    print('Into DescribeEc2Instance')
    instances = ec2.describe_instances(Filters=[{'Name': 'instance-type', 'Values': ["t2.micro", "t3.micro"]}])
    print(instances)

Output is

START RequestId: bb4e9b27-db8e-49fe-85ef-e26ae53f1308 Version: $LATEST
Into DescribeEc2Instance
{'Reservations': [{'Groups': [], 'Instances': [{'AmiLaunchIndex': 0, 'ImageId': 'ami-052c08d70def62', 'InstanceId': 'i-0a22a6209740df', 'InstanceType': 't2.micro', 'KeyName': 'testserver', 'LaunchTime': datetime.datetime(2020, 11, 12, 8, 11, 43, tzinfo=tzlocal()), 'Monitoring': {'State': 'disabled'}

Now to strip instance id from above output, I have added below code(last 2 lines) and for some reason its not working.

import boto3
region = 'ap-south-1'
instance = []
ec2 = boto3.client('ec2', region_name=region)

    def lambda_handler(event, context):
        print('Into DescribeEc2Instance')
        instances = ec2.describe_instances(Filters=[{'Name': 'instance-type', 'Values': ["t2.micro", "t3.micro"]}])
        print(instances)
        for ins_id in instances['Instances']:
                print(ins_id['InstanceId'])

Error is

{
  "errorMessage": "'Instances'",
  "errorType": "KeyError",
  "stackTrace": [
    "  File \"/var/task/lambda_function.py\", line 10, in lambda_handler\n    for ins_id in instances['Instances']:\n"
  ]
}

Answer 1

The loop iteration should be

for ins_id in instances['Reservations'][0]['Instances']:

since you have a Reservation key at the top level, then an array and objects in the array with the Instances key which itself is yet another array that you then actually iterate.